Integrated circuit devices may rely on one or more power supplies to provide operating power. Power supply voltages VCC and ground may be supplied to multiple locations within an integrated circuit to provide the operating power. The connections to these power supply voltages, as well as the circuitry used to produce the power supply voltages, may provide capacitance and resistance associated with the power supply voltages. Accordingly, the power supply voltages are not ideal. When multiple circuits coupled to the power supply voltages switch simultaneously, the load on the power supply voltage supply itself may cause the power supply voltage to shift, a phenomenon known as simultaneous switching output noise.
Prior systems address the problem of simultaneous switching output noise through data bus inversion, where the data is inverted at times in an attempt to balance the number of 1s and 0s communicated or through minimizing the number of transitioning signals during the communication. However, data bus inversion requires an additional output to indicate when the data is inverted, and when it is not. Moreover, it may require extra high speed data process logic with high power consumption; which may limit practical usage at high speed applications due to the shrinking timing budget for bus inversion processing data.
Still other prior systems address the problem of simultaneous switching output noise by coupling a capacitor and resistor to an output node of a circuit. When the output voltage overshoots a target output voltage, the capacitor stores the overshoot energy. When the output voltage undershoots the target output voltage, the capacitor may release energy. However, this approach is limited in that it addresses over- and under-shoots in a circuit output voltage and requires that the output node be coupled to a capacitor and resistor. The approach does not address reducing noise in the power supply voltages themselves, only the downstream effect at the circuit's output node. It may not be suitable for wide spread data output distribution, where uniformity among all DQs are specified with phase noise is different at various locations.